In which we explore the options for getting round Bristol (*), and the consequences of those decisions.
(*) Excluding Fishponds.

Saturday, 4 November 2017

Volvo bug reports, issue #1: MGIF driver

Given some of the Volvo self driving car developers are ex colleagues of Bristol Traffic team members, we get to file bug reports. Not some directly accessible issue tracker where you get to file stuff like "XC90 driver nearly killed me" only for tech support to close as a "works as intended", but at least get to give them cues about how their land-barges get used and abused in the field. Here's one of this week's Volvos. Mid-afternoon, not rush hour but within range of school pickup times. Sunny days to treasure before the miserable season settles in.

First: "MGIF" , "Must Get In Front"

Definition: A driver who is focused on overtaking the bike without looking ahead to consider "What happens next?

In AI terminology a "planning horizon of 1", usually loses to any computerised chess/draughts player with a horizon >= 2 unless the latter is awful about assessing the value of all enumerated moves & countermoves.

In this instance,

the speed limit of the bridge and the rest of the city for the subsequent 1-2+ miles in any direction is 20 mph. You can see one of the signs at 0:01 in the video

the cyclist she chooses to pass is doing 19-20 mph, still accelerating in their underresponsive steel-framed MTB.

The car a safe stopping distance in front is also doing 20 mph

And it'll have to slow down once it gets to the end of the bridge due to the road there (i.e it's 100% predictable, irrespective of time of day & pedestrian/traffic numbers)

the oncoming cyclist is going 15 + mph

Which means that

(a) there's no defensible reason to pass the cyclist "I need to break the law to overtake a bike cycling at the speed limit to get behind the other vehicle going at the same speed before I get into the city proper and really have to slow down".

(b) she's failed to anticipate how long it will take to overtake the bike, even as she speeds up to 25-30.

(c) the closure rate with the oncoming cyclist becomes about 40-45 mph. If the oncoming roadie hadn't been keeping to the far left of the lane, there'd have been a collision.

Looking back at the footage, she's hanging back at the split to two lanes at the tolls to make a late-binding choice of which one to go through -a slight sign of impatience. She takes the left one; the right hand one is occupied by an SUV whose driver can barely see over the wheel, which is why the cyclist chose to hang back and wait: didn't seem safe to go ahead. As the Volvo comes through fairly rapidly, it's probable she has one of the contactless cards which you top up with prepaid bridge crossing tokens; sign of a regular user. Given time of day, perhaps a resident of N. Somerset doing a late pickup of a child from somewhere in Clifton, someone who cannot afford to be held up by any vehicle doing the speed limit.

Now, what is he dev team planning w.r.t. oncoming collision avoidance, where it assesses oncoming velocity of the approaching vehicle, adds with its own and estimates time-to-impact, so perhaps suggesting some alternate actions? And what to suggest? There's the "massively accelerate, swing in hard and then brake" strategy, which is an extension of this drivers decision (and essentially a reward), the alternative is: brake, swing behind the cyclist they tried to pass, put it off. Which is safer, but not generally that common amongst "legacy" manual-drivers. There's some psychological "we're committed now" decision which interferes with the more rational "braking to survive is a good idea" strategy.

enjoy

P.S. UK DVLA now gives MOT history over time: https://www.check-mot.service.gov.uk ...you can see that GP05RZE used to be a 3K/y child seat equipped barge of Hendon, NW London, then over to bristol to do 15K/y. Where you can see from the repeated warnings "pitted/scored disks, front headlamp deterioration" that the owner doesn't actually do any maintenance. Probably not a good sign. Almost as bad as a MkI Golf GTi with the wheels coming off..